1. Field of the Invention
This disclosure relates to systems and methods for stabilization of human spines, and, more particularly, to instruments for inserting spinal implants for lumbar interbody fusion devices.
2. Description of the Related Art
The human spine is a complex structure designed to achieve a myriad of tasks, many of them of a complex kinematic nature. The spinal vertebrae allow the spine to flex in three axes of movement relative to the portion of the spine in motion. These axes include the horizontal (bending either forward/anterior or aft/posterior), roll (lateral bending to either left or right side) and rotation (twisting of the shoulders relative to the pelvis).
The intervertebral spacing (between neighboring vertebrae) in a healthy spine is maintained by a compressible and somewhat elastic disc. The disc serves to allow the spine to move about the various axes of rotation and through the various arcs and movements required for normal mobility. The elasticity of the disc maintains spacing between the vertebrae, allowing room or clearance for compression of neighboring vertebrae, during flexion and lateral bending of the spine. In addition, the disc allows relative rotation about the vertical axis of neighboring vertebrae, allowing the twisting of the shoulders relative to the hips and pelvis. Clearance between neighboring vertebrae maintained by a healthy disc is also important to allow nerves from the spinal chord to extend out of the spine, between neighboring vertebrae, without being squeezed or impinged by the vertebrae.
In situations (based upon injury or otherwise) where a disc is not functioning properly, the inter-vertebral disc tends to compress, and in doing so pressure is exerted on nerves extending from the spinal cord by this reduced inter-vertebral spacing. Various other types of nerve problems may be experienced in the spine, such as exiting nerve root compression in neural foramen, passing nerve root compression, and enervated annulus (where nerves grow into a cracked/compromised annulus, causing pain every time the disc/annulus is compressed), as examples. Many medical procedures have been devised to alleviate such nerve compression and the pain that results from nerve pressure. Many of these procedures revolve around attempts to prevent the vertebrae from moving too close to each other by surgically removing an improperly functioning disc and replacing it with a lumbar interbody fusion device (“LIF”). Although prior interbody devices, including LIF cage devices, can be effective at improving patient condition, the vertebrae of the spine, body organs, the spinal cord, other nerves, and other adjacent bodily structures make it difficult to obtain surgical access to the location between the vertebrae where the LIF cage is to be installed.
Generally speaking, using a less invasive surgical technique for a spinal surgical procedure will minimize trauma to the surrounding bone, tissues and muscle and improve patient condition after the surgery. However, the size of the LIF cage itself often dictates a relatively large size for the required surgical opening. Accordingly, it would be desirable to reduce the size of the LIF cage to minimize the size for the required surgical opening for installation of the LIF cage, while maintaining high strength, durability and reliability of the LIF cage device. Furthermore, it would also be desirable to design instruments for delivering these types of spinal implants. Instruments that can minimize trauma to the patient and can deliver these spinal implants accurately and precisely will be desirable.